The difference of 244 tons per acre of ground shown by the analyses is quite sufficient to account for the observed difference in the cultural result. The cause of this difference was that in the _uncultivated_ field there was a compacted surface-layer of several inches in thickness, which forcibly abstracted the moisture from the substrata and evaporated it from its surface; while the loose surface soil on the _cultivated_ ground was unable to take any moisture from the denser subsoil. [Illustration: Cultivated.] [Illustration: Uncultivated. FIGS. 48, 49.—Apricot Trees, Creek Bench Land, at Niles, Cal.] [Illustration: FIG. 50.—New Growth and Fruit on Trees, Cultivated and Uncultivated. Creek Bench Land at Niles, Cal.] The cultural results were that on the cultivated ground the trees made about three feet of annual growth, and the fruit was of good, normal size; while the trees in the uncultivated ground made barely three inches of growth, and the fruit was stunted and wholly unsaleable. It may be added that when, instructed by the season’s experience, the owner of the “uncultivated” orchard cultivated deeply the following season, his trees showed as good growth and fruit as his neighbor’s. EVAPORATION THROUGH THE ROOTS AND LEAVES OF PLANTS. Undesirable as is the evaporation from the surface of the soil, under all but exceptional conditions the evaporation from the leaves of plants is one of the essential functions of vegetable development. Not only because water serves as the vehicle of the plant-food absorbed by the roots and to be organized by and redistributed from the leaves, and the aeration occurring in the latter must of necessity result in a certain degree of evaporation; but largely because the conversion of liquid water into vapor serves to prevent an injurious rise of temperature in the leaves under the influence of hot sunshine and dry air. It is undoubtedly for the latter purpose that the greater part of the enormous amount of water required, as above stated (chap. 11) for the production of one part of dry substance, is actually used. When sufficient water to supply the required evaporation through the leaves cannot be brought up from the soil, the plant begins to wilt; or in the case of some plants with very thin and soft leaves the blade normally begins to droop during the hottest hours of the day; thus escaping excessive exposure to the sun’s rays, and recovering their turgor later in the afternoon. The amount of water actually evaporated from orchard trees has unfortunately not been directly determined, the investigations made in this respect having borne mainly upon forest trees. The Austrian Forest Experiment Station made a series of elaborate investigations on this subject in 1878, and the following data (quoted from the Report of the U. S. Dep’t of Agriculture for 1889) convey some idea of the results.